Red Flags
Make sure the water is warm—but not hot!

Questions to Ask
Ask children if the cold water reminds them of anything else. What about the hot? Before they add the color to the clear water, ask what they predict will happen to the water and to the color. Which bottle mixes up faster? When is the color darkest?

Tips for Less Mess
Whenever children explore with food color, old clothes or smocks are beneficial. Cover the work surface with newspaper, old towels, or a sheet. Have paper towels and a garbage bag handy.

Science Connection
The pigment/color molecules are closely packed together in their drop. As the color spreads out, the color molecules mix with the water. This process is known as diffusion. The color molecules eventually are evenly dispersed or mixed with the water molecules. Because of diffusion, a uniform shade of the color mixture is created.

To explore the movement of drops of color in bottles filled with cold and warm water.

What You Need

  • 2 clear plastic bottles (with caps) per child
  • Food coloring
  • Water

    What to Do
    Have children fill one bottle with very cold water and the other with warm water. At the same time, place two or three drops of the same color in each bottle. Watch what happens.

    Diffusion: The movement of molecules from one place to another, tending to create a uniform mixture.

    Try This
    Use two different colors in the bottles. What happens? Try using a different liquid. What would happen to milk? Add glitter or colored sand to the bottle. Secure tightly and shake. What happens?

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